Po-210 and Pb-210 in water and fish from Taboshar uranium mining Pit Lake, Tajikistan.

Polonium-210 in water and (210)Pb and (210)Po in different fish organs from 3 different fish species in Taboshar Pit Lake (n = 13), located in the uranium mining area in Tajikistan, and in Kairakkum Reservoir (reference lake, n = 3), have been determined as part of a Joint project between Norway, Kazakhstan, Kyrgyzstan and Tajikistan. The average activity concentration of (210)Pb and (210)Po in liver, muscle and bone of Carassius auratus was higher than the concentration in similar tissues of C. carpio and Sander lucioperca from the reference site. The accumulation of (210)Po was higher than for (210)Pb, and the accumulation of (210)Po was highest in the liver of C. auratus (3673 ± 434 Bq kg(-1) ww). Although the average activity concentration of (210)Pb in liver and bones of C. auratus from Pit Lake were fairly similar, a huge variation in the liver activity concentrations (25-327 Bq kg(-1) ww) was found. The results confirm direct uptake of unsupported (210)Po into the liver, and that the distributions of (210)Po and (210)Pb in fish organs were different. The BCF (L/kg) for (210)Po in bone, liver and muscle clearly demonstrates high accumulation of (210)Po in C. auratus, especially in the liver. The average BCFs of liver, bone and muscle were >1.4 × 10(5), >2.5 × 10(4) and >1.4 × 10(4), respectively. All fish in the Pit Lake were found to be in the same trophic level, however, a linear correlation between log (210)Po in liver and δ(15)N could indicate biomagnification of (210)Po in liver of C. auratus. In regards to the recommended Annual Limit of Intake (ALI) for (210)Po, the concentration of (210)Po in muscle tissues of C. auratus is alarming, as there is a high probability for the local population at risk to exceed the recommended ALI through consumption of fish from Taboshar Pit Lake.

Environmental impact assessment of radionuclide and metal contamination at the former U sites Taboshar and Digmai, Tajikistan.

Uranium (U) ore mining and processing were initiated in the former Soviet Republics of Tajikistan after the Second World War as part of the USSR nuclear weapon programme. The U mine in Taboshar was opened in 1936, and mining took place from 1945 to 1965, while the Digmai tailings dump was exploited during 1963-1993. The mining, milling and extraction activities have resulted in large amounts of waste rock deposits and U tailing materials placed in the vicinity of inhabited areas. To assess the environmental impact of radionuclides and trace metals in the Taboshar and Digmai mining and tailing sites in Tajikistan, field expeditions were performed in 2006 and 2008. In addition to in situ gamma and radon dose rate measurements, sampling of water, fish, sediments, soils and vegetation including in situ fractionation of water were performed. The U concentrations in water from Taboshar Pit Lake (2.0 mg U/L) were higher than in waters collected in the Digmai area. The Pit Lake and the stream water from the tailing mountain were also characterised by elevated concentrations of As, Mo, Mn and Fe, exceeding the WHO recommended values for drinking water. Uranium, As, Mo and Ni were present as low molecular mass species in the waters, and are therefore considered mobile and potentially bioavailable. The (238)U concentrations in sediments and soils varied between the sites; with peak concentrations (6 kBq/kg dw) in sediments from the Pit Lake, while the soil concentrations were significantly lower (296-590 Bq/kg dw). In contrast, high levels of the radium isotopes ((226)Ra and (228)Ra) were found in the Digmai soil (17-32 kBq/kg dw). Based on sequential extraction results, both U and Pb were found to be quite mobile at the Pit Lake site, showing that these elements were associated with the pH sensitive and redox sensitive amorphous fractions. In tailings, U was found to be quite mobile, but here Pb was rather inert. The transfer of radionuclides and metals from sediments to waters was in general low. In the Pit Lake, U was quite mobile (Kd = 90 L/kg), followed by Ni (1.5 × 10(3) L/kg) and As (6 × 10(3) L/kg), Cu and Cd (1.5 × 10(4) L/kg), while Pb (3 × 10(5) L/kg) was rather inert. The transfer from soil to plant, TFs (kg/kg dw), was in general low, while the bioconcentration factor for water living Poaceae and for fish from water was relatively high (Pb 1.8 × 10(5) and Cd 1 × 10(4)). These legacy sites, containing enhanced levels of natural radioactive material (TENORM) as well as heavy metals, may represent a hazard having a potential radiological and chemical impact on man and the environment, and measures should be taken to reduce the environmental risk to man and biota.

Uranium activity ratio in water and fish from pit lakes in Kurday, Kazakhstan and Taboshar, Tajikistan.

Kurday in Kazhakstan and Taboshar in Tajikistan were U mining sites operated during the 1950s and 1960s as part of the USSR nuclear weapon program. Today, they represent sources of potential U contamination of the environment. Within both mining sites, open pits from which U ore was extracted have been filled with water due to ground water inflow and precipitation. These artificial pit lakes contain fish consumed occasionally by the local people, and wild and domestic animals are using the water for drinking purposes. To assess the potential impact from U in these pit lakes, field work was performed in 2006 in Kurday and 2006 and 2008 in Taboshar. Results show that the U concentration in the lake waters were relatively high, about 1 mg/L in Kurday Pit Lake and about 3 mg/L in Taboshar Pit Lake. The influence of U-bearing materials on the lakes and downstream waters were investigated by measuring the U concentration and the (234)U/(238)U activity ratios. In both Kurday and Taboshar, the ratios increased distinctively from about 1 at the pit lakes to >1.5 far downstream the lakes. The concentrations of (238)U in gill, liver, muscle and bones in fish from the pit lakes were much higher than in the reference fish. Peak concentration of U was seen in bones (13 mg/kg w.w.), kidney (9.1 mg/kg w.w.) and gills (8.9 mg/kg w.w.) from Cyprinus auratus caught in the Taboshar Pit Lake. Bioconcentration factors (BCF) calculated for organs from fish caught in the Taboshar Pit Lake, with the same tendency seen in the Kurday Pit Lake, showed that U accumulates most in bone (BCF = 4.8 L/kg w.w.), gills (BCF = 3.6 L/kg w.w.), kidney (BCF = 3.6 L/kg w.w.), and liver (BCF = 2.5 L/kg w.w.), while least was accumulated in the muscle (BCF = 0.12 L/kg w.w.).

Acute and sub-lethal effects in juvenile Atlantic salmon exposed to low µg/L concentrations of Ag nanoparticles.

Silver nanoparticles (Ag-NP) are components in numerous commercial products and are discharged into the environment in quantities that are largely unknown. In the present study, juvenile Atlantic salmon were exposed to 1, 20, and 100 µg/L (48 h, static renewal) of a commercially available Ag-NP colloidal suspension in natural (soft) lake water. A solution of AgNO(3) containing 20 µg/L Ag(I) ions was also included to discriminate the effect of NPs from that of ionic silver. Furthermore, the commercial Ag-NP suspension was compared to an in-house synthesised colloidal NP suspension prepared from AgNO(3) and NaBH(4) in citrate buffer. The size distribution of Ag in all exposure solutions was characterised by 0.22 µm filtration and 10 kDa hollow fibre cross-flow ultrafiltration in combination with ICP-MS. All exposures were characterised by a relatively high proportion of Ag-NP in the colloidal size fraction 3-220 nm. For assessment of biological effects, acute toxicity, gill histopathology, blood plasma parameters (Na, Cl, glucose, haemoglobin), and gene expression of a selection of gill biomarkers were measured. Results showed that the gills accumulated Ag in all exposure groups apart from the fish exposed to 1 µg/L Ag-NP. Accumulated Ag caused concentration-dependent response increases in general stress markers such as plasma glucose and gill gene expression of heat shock protein 70. Furthermore, induction of the metallothionein A gene indicated that Ag had been internalized in the gills, whereas a concentration-dependant inhibition of Na/K ATPase expression indicated impaired osmoregulation at as low as 20 µg/L concentrations of Ag-NP. The commercial Ag-NP suspension caused acute gill lamellae necrosis at high concentrations (100 µg/L), potentially giving rise to the substantial (73%) fish mortality at this concentration. The two different Ag-NP preparations gave comparable results for several endpoints measured, but differed in MT-A induction and mortality, thus emphasising the variation in effects that may arise from different Ag-NP preparations.

Effects of combined gamma-irradiation and metal (Al+Cd) exposures in Atlantic salmon (Salmo salar L.).

These experiments were designed to investigate transcriptional effects in Atlantic salmon (Salmo salar) after exposure in vivo to ionizing gamma radiation combined with subtoxic levels of aluminum (Al) and cadmium (Cd). Juvenile fish (35 g) in freshwater with or without Al and Cd (255 microg Al/L + 6 microg Cd/L) were exposed to a 75 mGy dose of gamma-irradiation, and induced responses were compared to those of controls. The transcriptional levels of eight genes encoding proteins known to respond to stress in fish were quantified in liver of fish exposed for 5 h to gamma radiation, to Al and Cd or to the combination of Al, Cd and gamma radiation. The studied genes were caspase 3B, caspase 6A, caspase 7, p53 (apoptosis), glutathione reductase (GR), phospholipid hydroperoxide glutathione peroxidase (GSH-Px), (oxidative stress), metallothionein (MT-A) (metal stress) and ubiquitin (Ubi) (protein degradation). The results showed that gamma-irradiation alone induced significant upregulation of caspase 6A, GR, GSH-Px, MT-A and Ubi compared to the control group, while 5 h exposure to Al+Cd alone did not induce any of the studied genes compared to the control. No significant upregulation of the series of investigated genes could be observed in fish exposed to gamma-irradiation in combination with Al+Cl. In conclusion, the results suggest that the presence of Al+Cd in the water counteracted the gamma-irradiation effect by modifying the transcription of genes encoding proteins involved in the defense mechanisms against free radicals in the cells.

Environmentally relevant mixed exposures to radiation and heavy metals induce measurable stress responses in Atlantic salmon.

These experiments were designed to identify stress effects in 3 key organs in Atlantic Salmon (Salmo salar, L.) after exposure in vivo to very low doses of radiation, and subtoxic levels of aluminum (Al) and cadmium (Cd) alone or in combination. Six fish per group were sacrificed after exposure and the anterior kidney, fin, and gill were dissected and sentfor assay of bystander signal production as a stress response end point. Radiation doses as low as 4 mGy delivered over 5 h, alone or in combination with Cd and/or Al, caused bystander signals to be produced in tissues harvested from in vivo exposed salmon. The effects vary among different organs and are not consistently additive or synergistic for a given treatment although gill cells do show high degrees of synergism between radiation and metal exposure. Data for individual fish did not suggest any systemic sensitivity to the stressors. Interestingly, the data for Cd suggest that lower toxicity is found when the metal is used in combination with radiation exposure. Expression of two proteins associated with survival responses (Bcl-2) or death responses (cmyc) after radiation was measured in the tissue cultures and showed a highly significant correlation with response outcome. The results, although complex, indicate that these stress signal responses may aid in the mechanistic investigation of mixed contaminant effects in fish exposed to metals and radiation.

Multiple stressor effects of radiation and metals in salmon (Salmo salar).

These experiments were designed to look at the cellular effects in key organs in Atlantic salmon (Salmo salar) after exposure in vivo to radiation and subtoxic levels of aluminum (Al) and cadmium (Cd), alone or in combination. Salmon (25g) were exposed to a single 0.5Gy dose of gamma-irradiation in water containing Cd, Al or Cd+Al. Three fish per group were sacrificed after 1h and the liver, pronephros, fin and gill of each was dissected. Small explants of each tissue were set up. After 2 days, the culture medium was harvested and filtered then placed on a reporter cell line for determination of stress signal activity (bystander effects). Radiation in combination with Cd and/or Al, caused bystander effects in tissues harvested from in vivo exposed salmon. The effects vary between different organs and are not consistently additive or synergistic for a given treatment. Tissue type appears to be critical. Liver cultures produce a toxic factor which is lethal to reporter cells, and therefore no liver data could be obtained. It is hoped that this stress signal response will prove to be a useful indicator of environmental stress in species inhabiting aquatic ecosystems.